Will the recently elected leader of the Social Democratic and Labour party become Northern Ireland's new Dr No? Specifically, will the South Belfast MP and family doctor say no to the SDLP's continued presence inside the five-party power-sharing coalition at Stormont?

This is the key question now facing Alasdair McDonnell and his embattled troops as they seek to carve out a survival strategy over the next few months: to be inside the tent or out; to offer the electorate something different other than crowing about the party's past record of promoting non-violent nationalism and historic compromise with unionism.

Over the last decade the party founded out of the civil rights movement by the likes of Gerry Fitt and John Hume has declined as a force within nationalism. Sinn Féin, having allowed the IRA to wither away and memories of the Troubles to fade, has stolen the party's clothes in a dramatic act of political cross-dressing.

Gerry Adams and his followers have established themselves as the number one nationalist party in Northern Ireland; a position following the last assembly elections that looks unassailable.

Sinn Féin is today seen as the key component in the power-sharing arrangement with the Democratic Unionist party. The republican party now talks the inclusive language the SDLP spouted for decades through the Troubles regarding unionists.

They even invite Presbyterian ministers these days to address Sinn Féin delegates when they used to cheer to the rafters of Dublin's Mansion House masked men reading out bellicose statements from the IRA army council not so long ago. In this role reversal the SDLP has looked increasingly old and irrelevant.

As for McDonnell, he may lack certain airs and graces but at least he is up for a fight. Having once been the team doctor of the Antrim Hurling team he understands the need to get in hard and dirty, and to try to score some points by any means necessary.

He knew this in the rough and tumble of hurling, the world's fastest sport played on grass. Instinctively he realises this too in that other sport of blood and guts called politics.

Yet McDonnell cannot hope to score victories over his opponents while his party remains part of the power-sharing executive administrating Northern Ireland.

During the leadership contest one of his rivals, the very able minister Alex Attwood, suggested that perhaps it was time for the SDLP to leave the devolved government and become the main opposition force in the parliament. It is an idea McDonnell should return to and soon.

At present the size of the opposition in the assembly is miniscule and divided. It comprises just three, including the leader of the anti-power sharing Traditional Unionist Voice, Jim Allister, and the Green party's sole representative, Steven Agnew.

Every major political party is in government, which many people already disillusioned with politics regard as a cynical carve-up on sectarian-cantonal lines.

The SDLP will probably not catch up with Sinn Féin again in terms of the race to become the leading force of northern nationalism. That contest has been run. But the party of Fitt, Hume, Mallon and McDonnell can create a new space for itself as the one that holds the administration to account, that offers people of all creeds an alternative, that turns the Stormont parliament into a truly democratic arena with a large and viable opposition bloc.

By saying no to the current arrangement, the SDLP may even win some new supporters among the mass of disaffected out there in Northern Ireland who are repelled from the ballot box at election time because there is no alternative to vote for.

Because that old anarchist adage urging people not to vote because only the government (always the same government) gets in currently rings true in post-agreement Northern Ireland.